JPS5923276B2 - Charge-controlled inkjet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charge-controlled ink jet recording apparatus, and particularly to a phase matching device that controls charge timing.

In recent years, inkjet recording devices have been increasingly used as computer output terminals or as devices for directly printing dates, serial numbers, etc. on products during the production process because they are capable of high-speed printing without contact.

This device supplies ink under pressure to the noise, which atomizes the ink by applying vibrations at a constant frequency.
At this time, a predetermined pattern is recorded on the recording material by appropriately charging the particles and electrically deflecting them. What is difficult here is how to adjust the charging to the timing of particle formation, which changes depending on temperature, pressure, etc. This will be explained in detail using FIGS. 1 and 2. FIG. 1 is a block diagram of the electrical system of an inkjet recording apparatus. When the output of the crystal oscillator 13 is applied to the vibrator 2 installed in the nozzle 1 through the amplifier 9, the pressurized ink in the nozzle 1 is ejected.
Become particulate. Particle formation is performed in synchronization with the excitation frequency of the vibrator 2, and when the output of the charging signal generating circuit 14 is applied to the charging electrode 4 through the amplifier 10 in synchronization with this, the ink particles 3 are charged. The charged ink particles 3 are deflected by a deflection electrode 5 connected to a high voltage power source 11 according to the amount of charge, and reach a predetermined position on the recording material T. Note that the vibrator 2 is constantly excited, and the ink particles 3
are continuously produced, but the ink particles 3 that do not contribute to recording are not charged and are therefore not deflected, but instead hit the gutter 6 and are collected. FIG. 2 shows the relationship between ink particle formation and charging in an inkjet recording apparatus based on the above principle.

Fig. 2 1 shows the excitation voltage of the vibrator 2, and Fig. 2 2 shows the charged electrode 4.
voltage. Since the ink particle formation is synchronized with the excitation frequency of the vibrator 2, l ink particles 3 are generated in one period.
is created. The ink particles 3 are charged when they are turned into particles. Therefore, it is necessary that the charging signal reaches its maximum value at the time of particle formation. That is, it must not be rising, falling, or not at all. FIG. 2 and 3 show the relationship between particle formation timing and dot miss rate. Here, the dot miss rate means that the ink droplets 3 do not reach a predetermined position on the recorded object 7. In other words, this is the rate at which normal charging is not achieved. It can be seen that when particles are formed at the rise and fall of the charging voltage as shown in FIG. 2, the dot miss rate becomes extremely high. In order to normally charge the ink with the charging voltage shown in FIG. 2, the timing of ink particle formation is limited to the range Q. The timing of particle formation changes depending on the pressure, physical properties, excitation voltage, temperature, etc. of the ink. Therefore, in order to always perform stable charging, it is necessary to detect the timing of particle formation and change the phase of the charging signal accordingly. In order to detect the atomization timing, the example shown in FIG. 1 is provided with a charge detector 7 that detects the charge of flying ink particles 3 by electrostatic induction. Through charging signal generation circuit 1
4, and the phase of the charging signal is controlled depending on the magnitude of the signal.

There are several known examples of this control means.

In order to achieve more stable charging, it is preferable to use a method of finely controlling the phase, but conventional methods have used analog control, which has the drawbacks of complex equipment and lack of reliability. On the other hand, a method has also been adopted in which two-phase charging signals, that is, charging signals with 180 degrees of difference in phase, are used because the device becomes simpler. However, since this method requires a wide stability region Q as shown in Figure 2, it has the drawbacks of shortening the rise and fall times of the charging voltage and increasing restrictions on the physical properties of the ink. . The charging voltage can reach several gigantic volts, and an expensive device is required to reduce the rise and fall times. In addition, in industrial quick-jet recording devices that are required to print on recording materials other than paper, such as cans and plastics, there are many types of inks and nozzle diameters, and imposing restrictions on these is a major drawback. Become. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, improve phase matching performance, provide stable charge to ink particles, and enable stable recording, while significantly improving phase margin. An object of the present invention is to provide a charge control type ic jet recording device that can alleviate restrictions on ink physical properties, nozzle characteristics, etc.

In order to achieve this object, the present invention changes the phase of a charging signal for searching for a separated phase during non-recording at regular intervals, and temporarily suspends recording during recording, and then The charge is applied to the ink particles starting from the phase again, the amount of charge on the ink droplet group at each phase is detected and stored, and when the search has completed one cycle, the separation phase is determined based on the memorized result, and this The method is characterized in that ink particles are charged and recorded at the determined separation phase.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 8.

In this embodiment, eight phases are matched. FIG. 3 is a block diagram of a charging signal generation circuit including phase matching.

20 is an oscillation circuit that oscillates at eight times the excitation frequency of the nozzle 1, and its output clock is frequency-divided by 1/8 from an octal counter 21 and applied to the vibrator 2 via the amplifier 9 to excite the nozzle 1. do.

Further, the output of the counter 21 is inputted to a comparison circuit 22,
It is compared with either the counter 24 output from the data selector 23 or the output of the register 25. counter 24
is an octal counter whose output indicates the phase being searched and is incremented by a phase switching signal G to be described later. On the other hand, the register 25 stores the particleization phase, and is updated every time the counter 24 completes one cycle, that is, reaches zero. In response to the print signal S, the data selector 23 outputs the output of the counter 24 during non-printing and the output of the register 25 during printing. First, non-printing will be explained.

When the counter 21 and the counter 24 match, the comparison circuit 22
A match signal D is output, and the 8-bit shift register 29 is set to a certain value. The set value is shifted by clock A (8f), and its output E is sequentially input to AND gate 36. 30 is a setting circuit for setting the magnitude of the charging signal for searching the particle phase;
It is powered by ANDGATE 36.

The output of the AND gate 36 passes through a data selector 37 which is switched by a print signal S similar to that described above, and is converted by a DA converter 38 into an analog voltage corresponding to a digital amount. This analog voltage is applied to the charging electrode 4 through an amplifier 10. Therefore, the charging signal F applied to the charging electrode 4 during non-printing to search for the particulate phase has a phase determined by the counter 24 and a pulse width determined by the value set in the shift register 29. The size is determined by the setting circuit 30. The charges charged to the ink particles 3 by the above-mentioned charging signal F are detected by a charge detector 8 shown in FIG. This detection signal is input to the binarization circuit 28 through the amplifier 12. It is assumed that the amplifier 12 has an integral characteristic so as to detect the amount of charge on a plurality of particles 3. The binarization circuit 28 converts the voltage signal H corresponding to the amount of charge into a binary value of "1" if it is above a certain value and "0" if it is below a certain value, and its output J is divided into 8 pits by the phase switching signal G. The signal is input to the shift register 27.

The phase switching signal G instructs to update the search phase, and is given by counting the output D of the comparator circuit 22 with a counter 31 in this embodiment. However, counter 31
Since it is set during printing, the phase switching signal G is output only during non-printing. The search phase is switched using the charged electrode 4.
The charged particles 3 reach the charge detector 8 and the amplifier 12
It is sufficient that the time is longer than the time required for the output H to stabilize. The search phases are sequentially switched by the above-described method, and after one cycle, the charging results of each phase are stored in the shift register 27.

This result is input to a particulate phase determination circuit 26, which will be described later, and the particulate phase is stored in the register 25. Next, the operation during printing will be explained.

When the print signal S is input, the data selector 23 is switched to the register 25, and the comparison circuit 22 outputs a match signal D every time the counter 21 matches the particleization phase.
; The output signal D is input to the counter 32, and its output is input to the counter 33. The counter 32 counts vertical dots, and the counter 33 counts horizontal dots. When printing characters of vertical T-dots and horizontal 5-dots, they are respectively
It becomes a quinary counter. The outputs of counters 32 and 33 are R
It is input to the character signal generation circuit 34 composed of OM etc.
A dot signal indicating the presence or absence of printing is output and input to the AND gate 35. The amount of charge on the ink droplets 3 is given by the counter 32, and the AND output of both is inputted to the DA converter 38 through the data selector 37. This output, like the tangential signal, is applied to the charging electrode through an amplifier 10 to charge the ink droplet 3. At this time, the pulse width of the charging signal becomes the period of the signal applied to the vibrator 2. Further, the phase is determined by the register 25 and does not change during printing. FIG. 4 is a timing diagram showing waveforms of various parts, and the signals correspond to those in FIG.

The excitation signal B is obtained by dividing the clock A by 1/8, and is converted into a sine wave signal by an amplifier 9 and applied to the vibrator 2. D.O.
~D7 is the output signal of the comparison circuit 22 when the O~7 phase, that is, the counter 24 is O~7. Similarly, EO-E7 is the output of the shift register 29. In this embodiment, the shift register 29 receives "00111100" by the match signal D.
5 is set, the search signal E is connected to the excitation signal B and 9.
05 phase is different, and the pulse width is 1/2 of the period. FO indicates a θ charging signal when O phase is not printed, and the broken line indicates a charging signal during O phase printing. In the present invention, the charging signal during non-printing is narrower than that during printing, and only needs to be at the center, and the pulse width itself is not limited.As described above, in order to properly charge the ink particles 3, , when the charging voltage is constant, preferably in the middle.

Now, assume that the ink is turned into particles at time P,
The method for determining the particle phase will be described. FIG. 5 is a timing diagram showing the phase search method.

A phase search is performed during non-printing when the print signal S is not input, the search is temporarily interrupted during printing, and when the print signal S disappears, the search is restarted from the interrupted phase. H is the output of the amplifier 12, and J is its binary output, which indicates the charging state of the ink particles 3. As can be seen from Figure 4,
Since charging is performed normally in phases 2 to 4, the detection output H will be high.However, in phases 1 and 5, since it is at the rising and falling of the charging signal, it will be lower than in the former, and in phases 0 and 6. phase,
In the 7-phase case, the charging number is zero and no charging occurs, so no detection output H is obtained. If this detection output is binarized using the threshold shown by the broken line, it will become a binarized output like J, which is 2 to 2.
4 phases is ``1''. Therefore, if it is 2 to 4 phases,
Printing can be performed normally with any phase, but in order to reduce the dot miss rate, it is preferable to use the three phases closest to the particle phase. Particulate phase determination circuit 2 shown in FIG. 3 in FIGS. 6 and 7
6 examples are shown below. FIG. 6 is an example using ROM.

The ROM 4O inputs the 8-bit output of the shift register 27 and outputs the 3-pit particle phase to the register 25. The RO is set so that the center value of the bits indicating "11" in the shift register 27 is output as 3 bits encoded.
If M4O is coded and triturated, the phase of particle formation can be easily determined. If the number of ``1'' is an even number, for example 4
In this case, it is sufficient to output either one of the central phases. This circuit can be constructed at low cost using commercially available elements. FIG. 7 shows an example in which processing is performed by arithmetic processing without using ROM. The contents of the shift register 27 are input, the processing circuit 41, the A register 42, and the B register 43 are used to obtain the particleization phase, which is output to the register 25. This processing procedure is shown in FIG. First, the contents of the shift register 27 are transferred to the A register 42. B register 43
A value obtained by rotating the A register 42 to the left by 1 bit is input into . Next, the AN of A register 42 and B register 43
Take D and put it in A register 42. In the B register 43, put the one rotated to the right, contrary to the previous one, AND the two in the same way as above, and put it in the A register 42. A
Since the number of "1" is now 1 in the register 42, it is encoded into a binary number and output to the register 25.In this method, even if there are more than 8 phases, the above procedure can be repeated, so It is more versatile than the ROM method.As described above, the present invention emits a phase search signal during non-printing, shifts the phase of this signal at regular intervals, and applies it to the ink droplets. Detects and stores the amount of charge on particles,
After completing one cycle, the ink droplet separation phase is determined based on the memorized results for each phase, and the ink droplets are charged and printed using this phase during printing. This improves phase matching performance and provides a stable charge to the ink particles. In addition, stable printing can be performed by giving a certain amount of force, and the phase margin can be greatly improved, so that restrictions on ink physical properties, nozzle characteristics, etc. can be relaxed.

Furthermore, even if the search is interrupted by a print signal, the search is restarted from the phase at which it was interrupted, so even if the non-printing period is short, it can be easily followed.

[Brief explanation of drawings]

FIG. 1 is an electrical system block diagram of a charge-controlled interjet recording device, FIG. 2 is a characteristic diagram showing the relationship between ink particle formation and charging, and FIG. 3 is a diagram of a charge-controlled interjet recording device according to an embodiment of the present invention. 4 and 5 are timing diagrams showing the signal waveforms of each part of the charging signal generation circuit shown in FIG. 3, and FIGS. 6 and 7 are block diagrams of the charging signal generation circuit of the jet recording device. FIG. 8 is a block diagram showing each example of the particle formation phase determination circuit, and FIG. 8 is an explanatory diagram showing the processing procedure of the particle formation phase determination circuit of FIG. 2... Vibrator, 4... Charged electrode, 8...
...Charge detector, 20...Oscillation circuit, 2
1, 24, 31, 32, 33... Counter, 2
2... Comparison circuit, 23, 37... Data selector, 25, 27, 29... Register,
26... Particle phase determination circuit, 28...
- Binarization circuit, 30...Setting circuit for determining the magnitude of the search charging signal, 34...Character signal generation circuit, 38...D-A converter.

Claims (1)

[Claims] 1. In a charge control type inkjet recording device that corrects the phase relationship between the separation timing of ink particles and the recording charge signal, the phase of the charge signal is changed at regular intervals to search for the separation phase during non-recording. The above search has been completed by means of temporarily interrupting recording and restarting from the phase at which it was interrupted after recording is completed and applying it to the ink particles, and means to detect and store the amount of charge on the ink droplet group at each phase. The ink droplet is characterized by comprising means for determining, based on the memorized result, approximately the center of a phase group in which normal charging is performed as a separated phase, and ink particles being charged and recorded at the determined separated phase. A charge-controlled inkjet recording device.